Index: ../trunk-jpl/src/m/classes/geometry.py
===================================================================
--- ../trunk-jpl/src/m/classes/geometry.py	(revision 26840)
+++ ../trunk-jpl/src/m/classes/geometry.py	(revision 26841)
@@ -60,7 +60,11 @@
     # }}}
 
     def marshall(self, prefix, md, fid):  # {{{
-        length_thickness = 1 if np.isnan(self.thickness) else len(self.thickness)
+        if isinstance(self.thickness, (list, np.ndarray)):
+            length_thickness = len(self.thickness)
+        else:
+            length_thickness = 1
+
         if (length_thickness == md.mesh.numberofvertices) or (length_thickness == md.mesh.numberofvertices + 1):
             WriteData(fid, prefix, 'object', self, 'fieldname', 'thickness', 'format', 'DoubleMat', 'mattype', 1, 'timeserieslength', md.mesh.numberofvertices + 1, 'yts', md.constants.yts)
         elif (length_thickness == md.mesh.numberofelements) or (length_thickness == md.mesh.numberofelements + 1):